Automatic Gain Compensation

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RJHollins
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Re: Automatic Gain Compensation

Post by RJHollins » Wed Jan 06, 2016 7:47 am

Not much left in the tank tonite folks. This flu is kicking b*tt.

I'll try later ... but let me leave it with this:

Think ..... PINK

8-)
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Re: Automatic Gain Compensation

Post by Mannymac » Wed Jan 06, 2016 9:11 pm

Thanks RJ, pleasure to read your thoughts!

Can't wait for PINK to arrive.
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Re: Automatic Gain Compensation

Post by RJHollins » Wed Jan 06, 2016 10:43 pm

hmm ...in this topic, we're speaking of another 'PINK'.
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Re: Automatic Gain Compensation

Post by RJHollins » Thu Jan 07, 2016 5:24 am

From where we left off ...

Let's finally cut to the chase.

We have our audio track. We've decided and set this track to -18dB RMS. Nothing special ... plenty of headroom.

2. We want to start slapping on some processing ... EQ, PreAmps, Tape, Comps, more EQ ... whatever ... but we have a list.

Now we need to MANAGE this list..... WHILE we continue working with it.

And because changes WILL be made in the FX list settings ... I need to QUICKLY get to UNITY GAIN, from one Insert to the Next, throughout the chain.

From our engineering toolbox, we call on 2 plugins [VST] to aid us.

1. VU meter of choice. I prefer KlangHelm VU meter. It can be scaled for most any desired operating level, AND has built in TRIM. Can work dual-mono or linked stereo. [handy for presets that have L/R balance mis-alignment.

2. PINK NOISE signal generator.
There are several 'flavors' of PINK. A bit of personal research is One's homework assignment.
I [in my personal bias] prefer the NOISE generator I assembled and use in my [N]ebula[V]irtual[C]ontroller software.
It has several functions and tones available, and can be easily set to a specific Output level [again, typically -18dB will show as 0VU on the KlangHelm ref:-18.
ON/OFF button. simple.

Aside: so as NOT to add complexity, but for disclosure, I also use a couple other 'gain structure A/B' comparing plugins. One is a free JS plugin from TB-Pro audio [A/B], the other is Ian Sheppard's 'PERCEPTION' plugin. These 2 utilities serve useful function and compliment the workflow. Plus ... I really like using them.

That's all the 'tools' needed. Basically 2 plugins.

Here's the workflow layout:
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Re: Automatic Gain Compensation

Post by basaristudios » Thu Jan 07, 2016 5:46 am

What do you use the noise for?
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Re: Automatic Gain Compensation

Post by kindafishy » Thu Jan 07, 2016 6:58 am

There is way too much complexity happening here for my simple mind.

Here's my simple approach calibrating a Nebula chain. It has never let me down, and it always sounds fantastic.

To a track or when creating a reusable chain:
1) Add a tone generator and set it to -18dB.
2) Follow with a Nebula instance loaded with a desired library.
3) Follow with VUMT.
4) Adjust the input/output controls of the mentioned Nebula instance so that VUMT once again shows -18dB

Repeat steps 2, 3 and 4 with each additional Nebula instance that is part of the chain. Just insert it after the previous Nebula instance.

Quick, easy and painless.

This sets up a well tuned and predictable starting point. Now as I mix and make adjustments to any of the Nebula instances in the chain, I watch a VUMT instance at the end of the chain to ensure that it stays consistent (a VUMT at the start of the chain can be used for comparison too). If an adjustment on an instance (say an EQ for example) puts it out, just adjust the output control of that instance to bring it back. This ensures the next instance is being hit in the same optimal range.

This has been working perfectly for me for a very long time.

Of course, this assumes that audio tracks are properly gain staged to begin with (and why would they not be?).

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Re: Automatic Gain Compensation

Post by RJHollins » Thu Jan 07, 2016 6:58 am

At the top of the track:

1. PINK NOISE generator
2. VU meter
3. Plug-In of choice
4. VU meter
5. Plugin of choice
6. VU

.... seeing a pattern.

The PINK generator is outputting our Ref -18dBfs, which will read 0dB on our VU meter [same scale].
This 1st VU is mainly to verify the generator output.

NOTE: Not all generators can be trusted.

So, we have several instances in the chain, maybe 3 Nebulas call 3 different bands. As we Cut/Boost, the Neb outputs will change. That change goes directly to the next insert, and so forth.

You Own testing of this will verify just how much gain change happens from one instance to the next. Do the test. Seeing is understanding.

OK ... we now want to balance the entire chain. FAST.

1. you may want to turn DOWN main monitor for this step [recommended].

2. Turn ON Pink generator. Verify output [-18].

3. go to next VU. Is Level Above/Below 0dB ?

4. Adjust TRIM back to 0dB.

5. Next VU ... Adjust to 0.

Turn OFF PINK, Bring Monitor level back to normal. Play Track.

Often times the difference can be quite 'interesting'. Key Point, you are now hearing the processed track through a balanced chain.

Each Instance is getting hit at nominal Ref= -18dBfs.

As the chain grows, same concept applies.

You COULD actually leave things as is, with a Plugin FOLLOWED by a compensation VU [TRIMMED].

Group the pair and move them about the chain as you wish.

But it is a bit messy/clumsy. agreed.

Now it comes down to personal workflow.

You can make OUTPUT level changes directly on the Nebula/Acqua plugin !
With the VU after the plugin ... put TRIM to ZERO [no gain change].

With PINK generating signal, view the tailing VU, but adjust the OUTPUT of Neb/Acqua so that VU reads 0VU.

Do this for the rest of the chain.

Now you have each NEB/ACQUA working at UNITY self contained. The KlangVU's can be bypassed.

A MODIFIED approach can be using only ONE monitoring VU meter. Slide the VU below each VST plugin, adjust plugin to 0dB ... slide VU below the next.

Step back ....

How One wants to do their layout is totally up to them. I've used all these variations.

After a while, you notice that certain presets ALWAYS need a touchup ... some Consoles and PreAmps for example. Because they have minimal to NO adjustments, I balance the OUTPUT dirctly on Nebula [viewing the Klang-VU], then bang the meter [don't usually need it for that instance again].

Here's the working issue.

If you are making adjustments [like EQ'ing], the plugin Output levels will change AND impact the next in the chain .... through to the end. So you may want to leave your monitoring VU's in place to allow a quick re-cal.

If you are going to RENDER a track, you may want to get rid of all the monitoring VU's, so just make the adjustments on the NEB OutPuts.

Lets stop.

This 'Gain Structure' balancing idea/technique seems to have it's beginnings before there was the written word. I can't verify this. It was something that just got passed along. Importantly ... it got you in the ballpark really fast.

Peek back in recording history to days of MANUAL setup. There was NO RECALL. Settings could be on paper or Polaroid B/W photos. Heck ... I seem to recall a session documented on an Etch-A-Sketch :shock:
Studio time could run $75 - $190+/hr.

Key point.

Again ... Quality ... whilst still maintaining sanity and control.

Being able the Gain Structure so efficiently that you would NOT hesitate to make an adjustment BECAUSE you can re-balance quickly.

Accuracy/tolerance.

The choice of PINK didn't just happen. It just seems to yield a good solution. Might a different 'noise' or combo 'burst' method give better results? Quite possible.

What I do know is that I want to hit a plugin with what it expects.
Once in that plugin, I want control to drive it HOT/COLD/ or NEUTRAL.
I MUST have that output back to Ref Level, so that the next plugin is ready. If I can FX order, I need complete freedom to do so WITHOUT levels changing.

UNITY GAIN: What goes IN = What goes OUT.

Closing.

By no means is this technique an 'absolute perfect' method. In fact ... when/if discrepancies ... they can be easily identified, and thereby manual 'modified' as engineering experience dictates.

Even through potential pitfalls/shortcomings I can easily state that the sonic IMPROVEMENTs I have A/B directly [using Nebula/Acquas] with a balanced change can yield remarkable results.

Now maybe some of the processing decisions might have to change BECAUSE of what just happened, but that is from engineering decision.

Now you can fine tweak, and quickly re-balance, allowing you to get to the prime mission.

LISTENING.

I hope some of this helps those new to the audio world, and particularly Nebula/Acqua users, as Gain Structure is much more relevant with this technology.

Of course ... this is all open for talk, discussion, ideas. Through my 'Robitussin' warped brain-cell, I've tried to present some point of reference and glimpse to a workable solution.

Sincerely
RJ
8-)
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Re: Automatic Gain Compensation

Post by basaristudios » Thu Jan 07, 2016 8:41 am

Nowadays VU are going extinct too, never Mix without a LUFS Meter which has a Momentary and Integrated Level on display plus you get the Benefit of Peaks, True Peaks and Dynamic Range, all in on. I have been using LUFS for quiet a while and since then i actually know my work improved. Before i used to have 5 different Meters on a track, LUFS changed everything, one Meter and its all there. Besides what i said above...back to topic...

One thing i do is, i place the VU on the first insert of every track but then only one VUMT on the first insert of the Master Track. What happens here is you avoid adding a VUMT after every plugin in the chain, while you Tweak the Effect processor on that Track you watch the Master VUMT and you adjust according to that...same as having it after the processor but here you do not have to have it everywhere, just one place.
Last edited by basaristudios on Thu Jan 07, 2016 8:47 am, edited 2 times in total.
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Re: Automatic Gain Compensation

Post by basaristudios » Thu Jan 07, 2016 8:43 am

RJHollins wrote:
1. you may want to turn DOWN main monitor for this step [recommended].

2. Turn ON Pink generator. Verify output [-18].

3. go to next VU. Is Level Above/Below 0dB ?

4. Adjust TRIM back to 0dB.

5. Next VU ... Adjust to 0.

Turn OFF PINK, Bring Monitor level back to normal. Play Track.
Now i read this again and understood why you use Pink Noise, good idea but still, time consuming and also not correct. Lets say you have a synth line, and runs thru the chain, then you adjust all the chain Volume with a Pink Noise, that is kinda impossible, Pink Noise and a Synth Line have different characteristics and harmonics and everything and also respond differently. If you Synth Line went 1db up because of EQ does not necessarily mean the Noise will go up 1 db, might go up 3 db or not at all. So you end up with incorrect Volume. Just adjust everything using the Sound that the track is already fed, not Pink noise. There is just no way to get around this...Lol. Until every plugin has correct Meters and a switch of Pre and Post.
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Re: Automatic Gain Compensation

Post by basaristudios » Thu Jan 07, 2016 8:49 am

RJHollins wrote:and particularly Nebula/Acqua users, as Gain Structure is much more relevant with this technology.
That is correct, i think all Nebula and Aqua stuff depends of what you feed into it and also there is quiet a few Algos that do this already, have to be fed certain level to show its true colors.
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Re: Automatic Gain Compensation

Post by basaristudios » Thu Jan 07, 2016 8:03 pm

I forgot to mention, if you go here:
http://www.tb-software.com/TBProAudio/download.html
Your life is set for LIFE! the AB LM and AGS will do everything
automated, Gain Staging and ABing while doing effects processing.
Will save you days of time and everything, its all automatic.
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Re: Automatic Gain Compensation

Post by RJHollins » Sat Jan 09, 2016 6:58 am

Let make things clear.

Before we globally dismiss everything from VU meters to a 'Gaining technique' ...

We've, seemingly, countless postings that ask about proper gain staging.

For many users working with plugins like Nebula/Acqua, we have questions of 'optimal' levels.

What I've try to present, in an INTENTIONALLY slowed down manner, giving the seeker of more experience opportunity to think through the concept/process.

2nd ... some of those asking MAY have not ever tested, or actually listened to their efx chain in a balanced status. Either confused by the whole process, or not heard to be appreciated.

Therefore ... we laid out an order, with 2 simple, easily available tools, that can be put into use.

Once the concept is experienced, there is nothing to stop one from customizing it to their need.

I would also take exception to points raised earlier.

Although we have new definitions in 'metering'. There is no official statement that the VU meter standard is to terminate. You may personally find that 'other' measurement tools better suite your purpose.

Keep in mind, neither hardware NOR plugins understand LUFS, R128, ITU BS1770, or ATSC A/85 .... these are perceived 'Loudness Units'.
Simply put, a VU meter is a 'Voltage' measurement.

These are 2 different systems, with specific goals intended. You could correlate them, but the user best understand the difference.
When we speak -18dB [RMS], this relates to a voltage measurement [VU], not a 'perceived' loudness.

Next. We used PINK noise for reason. We did NOT use WHITE noise ... again for reason. And, a 1 kilohertz test tone, famous for specific calibration, is not considered appropriate for covering full bandwidth potentials. It does have importance in other calibrating needs.

Lets not forget ... some audio sources are DYNAMIC. Their levels will vary over time.

We know that LOW FREQUENCIES can impact LEVEL much more than HIGH FREQUENCIES might. Easy to test and verify. Do it so you see the impact. This is why PINK was chosen.

Is this the BEST solution. No one said that.

There ARE calibration tones that challenge the entire spectrum. Anyone familiar with calibration programs like IK's 'ARC', or Home Theatre's 'REW' app use a special, spectral, CHIRP. These tend to NOT be practical to the mixing/mastering engineer in his/her routine workflow.

As to efficiency.
That depends on how many plugs in the chain. We've talking a couple seconds per plugin ... so many 20-30 secs to change EVERY plugin output. If you only changed settings in 1 or 2 plugs, then ONLY those need to be re-balanced ... so maybe 5 secs :lol:

Points to be mindful of:

If you read the documentation included with 'other' plugin manufacturers that use a form of 'Automatic Gain Compensation', they often suggests turning OFF the AGC function when RENDERING tracks, reminding the User that these AGC are best 'guess' at correction.

THOUGHTS:

Proper Gain Structure is important. It can be one of the most tedious aspects to the gig.

The digital world of DAW's has opened near unlimited possibilities, combinations. But they also host a magnitude of signal maintenance that can easily be hidden from view in an effects chain list.
In the pure 'hardware' daze, we did things in stages. We also had commitments to make with available hardware units or tracks on the tape machine. We had lights, meters, indicators, and knobs, that flashed and blinked, etc.

Today, with a strong enough computer, we have a real-time processing list that can take a source from RAW through to every emulation. Then we can change are mind.

That flexibility is also the challenge for the mundane task of proper gain structuring.

Looking to a computer solution, and AGC ... I wonder, is the solution to be had at the plugin itself ... or would this better be served from the DAW FXChain protocol itself. Were EACH FX slot could be monitored and compared, then optionally UNITY BALANCED. I wonder.

Utilities like TBProAudio A/B, Ian Sheppard 'Perception', and others, have helped to address. But they too look at a 'perceived loudness' [maybe not of significant issue]. I have and use BOTH these utilities, but find they help to address OTHER important comparison issues.

I want plugin to plugin unity gain balance. Inside the plugin, we can 'cook' or 'lean out', but its output should return to unity gain in the chain.

In my personal 'programming' hobbies, beside making NVC MIDI controllers for custom Nebulas [AlexB's MMeQ is already in the works], I've been pondering a 'meter bridge' concept that would aid the engineer in this specific task. I want less distraction opening closing windows, and a more productive workflow to critical listening.

Hey ... for those that have their system working for them. Excellent.
These are ideas for those that want to get a handle on this. Particularly with Nebula and Acqua.

I hope this gives some ideas to that path.
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Re: Automatic Gain Compensation

Post by basaristudios » Sat Jan 09, 2016 8:01 am

Man, forget all this...tell us...are you still taking drugs?...i mean NyQuill...lol...anything better?
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Re: Automatic Gain Compensation

Post by RJHollins » Sat Jan 09, 2016 8:28 am

Excuse me ... do you have some kind of problem ?
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Re: Automatic Gain Compensation

Post by NoNameComesInMind » Sat Jan 09, 2016 3:55 pm

not to jump in and start anything, but it seems what Rj is implying is just a very conservative and concise way of doing things as a helpful tool, i actually do this myself (but without noise generator since i'm an hobbyist and can pick and choose perfectly recorded samples to my liking) but mainly because it allows for linear damage control, since Nebula/acqua's behaviour is realtime dynamics; level matching will be a nightmare if you need to repair something later on, you don't want extremes or lows that either kickstart the kernel engine to activate a higher kernel, or shuts of the 3d imagery completely, it just doesn't sound natural in my own experience.

now for the inputs/outputs he also stated that input/output + trim they are all drive controllers in the case of nebula, having unity gain, allows for the choice of coloration and or dimension later on.

when you stop forcing your acqua/nebula you'll experience the true beauty of it :mrgreen:
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